Fix flakiness during import of a cache with empty layers removed

cache/remotecache/v1/cachestorage.go

@@ -214,35 +214,41 @@ func (cs *cacheResultStorage) Save(res solver.Result, createdAt time.Time) (solv
 }
 
 func (cs *cacheResultStorage) LoadWithParents(ctx context.Context, res solver.CacheResult) (map[string]solver.Result, error) {
-	v := cs.byResultID(res.ID)
-	if v == nil || v.result == nil {
-		return nil, errors.WithStack(solver.ErrNotFound)
-	}
-
 	m := map[string]solver.Result{}
 
 	visited := make(map[*item]struct{})
-	if err := v.walkAllResults(func(i *item) error {
-		if i.result == nil {
-			return nil
-		}
-		id, ok := cs.byItem[i]
-		if !ok {
-			return nil
-		}
-		if isSubRemote(*i.result, *v.result) {
-			ref, err := cs.w.FromRemote(ctx, i.result)
-			if err != nil {
-				return err
+
+	ids, ok := cs.byResult[res.ID]
+	if !ok || len(ids) == 0 {
+		return nil, errors.WithStack(solver.ErrNotFound)
+	}
+
+	for id := range ids {
+		v, ok := cs.byID[id]
+		if ok && v.result != nil {
+			if err := v.walkAllResults(func(i *item) error {
+				if i.result == nil {
+					return nil
+				}
+				id, ok := cs.byItem[i]
+				if !ok {
+					return nil
+				}
+				if isSubRemote(*i.result, *v.result) {
+					ref, err := cs.w.FromRemote(ctx, i.result)
+					if err != nil {
+						return err
+					}
+					m[id] = worker.NewWorkerRefResult(ref, cs.w)
+				}
+				return nil
+			}, visited); err != nil {
+				for _, v := range m {
+					v.Release(context.TODO())
+				}
+				return nil, err
 			}
-			m[id] = worker.NewWorkerRefResult(ref, cs.w)
-		}
-		return nil
-	}, visited); err != nil {
-		for _, v := range m {
-			v.Release(context.TODO())
 		}
-		return nil, err
 	}
 
 	return m, nil